Various organometallic precursors are used to form high-κ dielectric thin metal films for use in the semiconductor industry. Various deposition processes are used to form metal-containing films, such as chemical vapor deposition (“CVD”) or atomic layer deposition (“ALD”), also known at atomic layer epitaxy. Organometallic precursors deposited by such chemical phase deposition processes have applications in nanotechnology and fabrication of semiconductor devices such as capacitor electrodes, gate electrodes, adhesive diffusion barriers and integrated circuits.
CVD is a chemical process whereby precursors are deposited on a substrate to form a solid thin film. In a typical CVD process, the precursors are passed over a substrate (wafer) within a low pressure or ambient pressure reaction chamber. The precursors react and/or decompose on the substrate surface creating a thin film of the desired material. Volatile byproducts are removed by gas flow through the reaction chamber. The deposition film thickness can be difficult to control because it depends on coordination of many parameters such as temperature, pressure, gas flow volumes and uniformity, chemical depletion effects and time.
ALD is a chemical process similar to CVD, except the ALD process separates the precursors during the reaction. The first precursor is passed over the substrate producing a monolayer on the substrate. Any excess unreacted precursor is pumped out of the reaction chamber. A second precursor is then passed over the substrate and reacts with the first precursor, forming a monolayer of film on the substrate surface. This cycle is repeated to create a film of desired thickness. ALD film growth is self-limited and based on surface reactions, creating uniform depositions that can be controlled at the nanometer scale.
Moss J., Mol. Catal. A: Chem., 107:169-174 (1996) reports an investigation and characterization of metal alkyl complexes of the type RMn(CO)5 (R=alkyl group) and CpM(CO)2R (Cp=η5-C5H5, M=Fe, Ru or Os), and binuclear complexes Cp(CO)2Ru(CH2)2Ru(CO)2Cp.
Current precursors for use in chemical phase deposition display low volatility, poor growth control and an inability to scale up. Therefore, there is a need for improved chemical phase deposition precursors, particularly for use in ALD and CVD, which display higher thermal stability, better adhesion, higher vapor pressure and carbon free layers.